Weak Spot in Internet Security Is Network of Makers, Sellers of Advertisements

Hackers increasingly are exploiting a little-discussed weak spot in Internet security: The byzantine network of ad makers and sellers that target online ads based on users' browsing habits.

The trend was reinforced recently when Yahoo Inc. displayed an advertisement laced with malicious computer code to European users for a week. Other major websites have run malicious ads in recent months, including those of newspapers, blogs and...

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Malware Viruses May Be Hiding in Online Ads

Hackers increasingly are exploiting a little-discussed weak spot in Internet security: The byzantine network of ad makers and sellers that place targeted ads on websites. Danny Yadron reports on digits.